The present invention relates to a method and apparatus for enabling the unambiguous identification of an analog television signal, and more particularly to the provision of tag data in a blanking interval of the analog television signal to associate the signal with information such as a channel name and number, program title and schedule information. The identifying information can then be decoded and displayed on a viewer""s television set. The invention is particularly suited for use with digital television receivers that are also capable of receiving analog television signals, and which include look up tables for identifying received television services and/or program guide data.
The following terms are defined:
ATSCxe2x80x94Advanced Television Systems Committee;
ATSC A/65xe2x80x94xe2x80x9cProgram and System Information Protocol for Terrestrial Broadcast and Cablexe2x80x9d standard of the ATSC;
DTVxe2x80x94Digital Television;
EIAxe2x80x94Electronic Industries Association;
EIA-608xe2x80x94EIA Standard xe2x80x9cRecommended Practice for Line 21 Data Service,xe2x80x9d ANSI/EIA-608-1994, September 1994, Arlington, Va.; see also xe2x80x9cSP-3688-1 Changes to EIA-608,xe2x80x9d Apr. 19, 1996;
EPGxe2x80x94Electronic Program Guide;
EITxe2x80x94Event Information Table;
ETTxe2x80x94Event Text Table;
MPEGxe2x80x94Moving Picture Experts Group;
N3xe2x80x94Naming, Numbering and Navigation;
NTSCxe2x80x94National Television Systems Committee;
PSIPxe2x80x94Program and System Information Protocol
TSID (digital)xe2x80x94Transport Stream ID (MPEG);
TSID (analog)xe2x80x94Transmission Signal ID;
VBIxe2x80x94Vertical Blanking Interval;
VCTxe2x80x94Virtual Channel Table;
CVCTxe2x80x94Cable VCT
TVCTxe2x80x94Terrestrial VCT; and
XDS (or EDS)xe2x80x94Extended Data Service.
Recently, there has been a rapid increase in the number of available television channels due to the advent of digital television transmission schemes such as MPEG-2 and Digicipher(copyright) II, the latter of which is proprietary to General Instrument Corporation, the assignee of the present invention. Background information for the MPEG-2 standard may be found in document ISO/IEC 13818-1 (MPEG-2), entitled xe2x80x9cGeneric Coding of Moving Pictures and Associated Audioxe2x80x9d, Part 1 (Systems), July, 1995, now ITU-T Recommendation H.222.0.
Digital compression techniques allow more than one television signal to fit into the transmission bandwidth occupied by a single analog transmission. In fact, with proposed schemes, up to ten or more standard definition television (SDTV) channels, or two high definition television (HDTV) channels can fit into the 6 MHz bandwidth which conventionally carries only one analog television channel.
At the present time, broadcasters have begun to augment their existing analog equipment to provide digital signal transmission, and television viewers will soon have the opportunity receive such signals by purchasing a new digital television receiver. Since it will obviously take an extended period of time to phase digital television into the mainstream and to phase analog television out, there will be many years where the provision of both analog and digital television will overlap.
Accordingly, there has been significant interest in television communication schemes where some of the channel allocations are used to provide digital television signals, while other allocations carry analog signals. The ATSC Digital Television System defined according to the ATSC A/65 Program and System Information Protocol is one such scheme. Background information may also be found in the document xe2x80x9cSystem Information for Digital Televisionxe2x80x94ATSC Standardxe2x80x9d, Doc. A/56. Jan. 3, 1996, Advanced Television Systems Committee. Such schemes are expected to provide a transition to an all-digital system by allowing terrestrial broadcasters and cable television system operators to continue transmitting their conventional analog television channel(s) while concurrently transmitting one or more new digital channels.
Although a digital receiver may use a digital signal""s TSID as defined in the MPEG-2 Systems standard to unambiguously identify the digital signal, prior to the present invention no equivalent ID tag was defined in the analog domain. Consequently, it has not been possible for receivers to positively identify each analog channel. As a result, digital data which is associated with the analog channel, such as channel name (e.g., station identifier), channel number, and program guide data, may be incorrect, thereby confusing the viewer. In particular, an analog channel which is not the one that would be expected to be recovered from a pre-assigned channel frequency may be received due to weather conditions, terrain, geographic location or antenna orientation, for example.
Accordingly, it would be advantageous to provide a system for positively and unambiguously identifying analog television services. It would be further advantageous to use the identification data to access information about the analog service, e.g., by reference to an appropriate look up table stored in the television receiver. Examples of such look up tables include a TVCT for providing channel name and number, an EIT to provide program titles and schedules, and an ETT for providing text, e.g., program descriptions. The data stored in the TVCT could then be used to provide an information display to the television viewer about the analog service, comparable to the information provided about digital television services through the use of a digital VCT.
The present invention provides a system having the above and other advantages.
The present invention relates to a method and apparatus for accurately and unambiguously identifying an analog television signal received via a terrestrial broadcast. In particular, the invention addresses the problem of naming, numbering and navigating (N3) where virtual channel tables (VCTs) are used to map user channels (e.g., programming services) to physical characteristics.
A terrestrial broadcast receiver obtains VCTs by acquiring digital transport streams and storing the VCT data carried in the transport stream. Each digital transport stream is assumed to be identified by a unique tag, such as transport_stream_ID (TSID) used in the MPEG-2 standard. A receiver may use the TSID by finding a transport stream and navigating using a VCT for that digital TSID.
As discussed herein, a VCT can be used to reference analog channels in addition to digital channels. A digital transport stream identifies itself by means of its digital TSID. The VCT references a given analog channel only by its frequency, so that if an analog channel other than the one referenced is actually received on that frequency, erroneous information will be provided to the viewer about the analog service actually received.
In accordance with the present invention, an equivalent tag to the digital TSID is supplied within the analog waveform. This analog tag is referred to herein as an analog TSID (transmission signal identifier), in contrast to a digital TSID (transport stream identifier), and can be carried, for example, in a blanking interval (horizontal or vertical) of the analog television signal.
A method in accordance with the invention unambiguously identifies an analog television programming service which is communicated from a transmitter to a receiver. A transmission signal identifier is assigned to the analog programming service. This identifier may comprise, for example, a field of bits that is sufficiently long to provide the necessary unique identifying information. In one embodiment, a 16-bit field is used, although it will appreciated that the invention is by no means limited to any specific number of bits used to provide the transmission signal identifier. Independently of the analog service, channel data is provided which correlates the analog transmission signal identifier to at least one service characteristic, such as the channel name, the title of the particular program event (e.g., television program title), and/or schedule information. The channel data may comprise, for example, data stored in a channel map, plus program event data stored in an electronic program guide (EPG) database (e.g., EIT and ETT).
The transmission signal identifier is inserted into the analog programming service (e.g., in the vertical blanking interval) for communication with the analog programming service to the receiver. The channel data is also communicated to the receiver, e.g., in a separate digital multiplex that also carries one or more digital television services.
At the receiver, the transmission signal identifier is recovered to identify the actual analog signal that has been received. The TSID is cross referenced in the VCT to obtain the channel data for the analog signal. The channel data thereby obtained is used to display information (i.e., service characteristics) about the analog programming service.
Comparable transport stream identifiers may also be assigned to the digital programming services. The digital TSIDs are similarly used to obtain associated channel data for the digital programming services. In this manner, service characteristics of the digital services can be displayed to the viewer.
A corresponding apparatus and receiver are also presented.